Zinc complexed insulin compound is commercially available, for example, under the trade names HUMULIN® and HUMALOG®. Zinc complexed insulin typically exists in a hexameric form. Various methods have been described for the use of zinc in the crystallization of acylated insulin. For example, U.S. Patent Publication 20010041786, published on 15 Nov. 2001, by Mark L. Brader et al., entitled “Stabilized acylated insulin formulations” describes a formulation with an aqueous solution for parenteral delivery, particularly as an injectable formulation, with a pH of 7.1 to 7.6, containing a fatty acid-acylated insulin or a fatty acid-acylated insulin analog and stabilized using zinc and preferably a phenolic compound. U.S. Pat. No. 6,451,970, issued on 17 Sep. 2002 to Schaffer et al., assigned to Novo Nordisk A/S, entitled “Peptide derivatives” describes derivatives of insulin compound and insulin analogs where the N-terminal amino group of the B-chain and/or the ε-amino group of Lys in position B28, B29 or B30 is acylated using long chain hydrocarbon group having from 12 to 22 carbon atoms and zinc complexes thereof.
Protamines and phenolic compounds have been described for use in the crystallization of acylated insulin. U.S. Pat. No. 6,268,335 (31 Jul. 2001) and U.S. Pat. No. 6,465,426 (10 Oct. 2002) to Brader, both entitled “Insoluble insulin compositions,” describe insoluble compositions comprised of acylated insulin a protamine complexing compound, a hexamer-stabilizing phenolic compound, and a divalent metal cation.
Existing approaches are especially tailored for crystallization of native insulin compound or insulin compound analogs or for acylated insulin compounds having increased lipophilicity relative to non-acylated insulin compounds. There is a need in the art for pharmaceutically acceptable complexes including derivatized insulin compounds, other than acylated insulin compound, such as hydrophilic and/or amphiphilic insulin compound derivatives, and for stabilizing non-acylated lipophilic insulin compound analogs. There is also a need in the art for new protein conjugates having increased bioavailability or other improved pharmaceutical attributes relative to existing conjugates. There is a need in the art for new formulations that facilitate oral delivery of proteins and protein conjugates. Finally, there is a need for a combined approach to improving the oral bioavailability of a protein, such as insulin compound, which incorporates an improved oral protein conjugate provided as a solid in an improved formulation to maximize the benefits for the oral delivery of proteins.